l1 nwt - ip addressing-revision

Network Troubleshooting CT046-3.5-3

IP Addressing - Revision

CT046-3-3 Network Troubleshooting IP Addressing Revision

192.168.10.0/24


VLSM

No of Host

Block Size

Bits borrowed Subnet Mask

Network Address

25 32 11100000 255.255.255.224 192.168.10.0/27

12 16 11110000 255.255.255.240 192.168.10.32/28

10 16 11110000 255.255.255.240 192.168.10.48/28

6 8 11111000 255.255.255.248 192.168.10.64/29

2 4 11111100 255.255.255.252 192.168.10.72/30

Class C Subnetting

Subnet Subnet Mask Network Address

1 255.255.255.224 192.168.10.0/27

2 255.255.255.224 192.168.10.32/27

3 255.255.255.224 192.168.10.64/27

4 255.255.255.224 192.168.10.96/27

5 255.255.255.224 192.168.10.128/27


VLSM Answer


Try This! 192.168.10.0/24


VLSM Answer


• No of subnets : 8• Highest no of host per subnet : 100 host (block size 128)

• What IP address to use for subnetting?• What is the Subnet Mask?• IP Addressing plan??

Try This!


Class B Subnetting (Solution A) – 172.16.0.0/16

Subnet Bits borrowed Subnet Mask Network Address

1 11100000.00000000 255.255.224.255 172.16.0.0/19

2 11100000.00000000 255.255.224.255 172.16.32.0/19

3 11100000.00000000 255.255.224.255 172.16.64.0/19

4 11100000.00000000 255.255.224.255 172.16.96.0/19

5 11100000.00000000 255.255.224.255 172.16.128.0/19

6 11100000.00000000 255.255.224.255 172.16.160.0/19

7 11100000.00000000 255.255.224.255 172.16.192.0/19

8 11100000.00000000 255.255.224.255 172.16.224.0/19

No of host per subnet : 213-2 = ???


Class B Subnetting (Solution B) – 172.16.0.0/16

Subnet Bits borrowed Subnet Mask Network Address

1 11111111.10000000 255.255.255.128 172.16.0.0/25

2 11111111.10000000 255.255.255.128 172.16.0.128/25

3 11111111.10000000 255.255.255.128 172.16.1.0/25

4 11111111.10000000 255.255.255.128 172.16.1.128/25

5 11111111.10000000 255.255.255.128 172.16.2.0/25

6 11111111.10000000 255.255.255.128 172.16.2.128/25

7 11111111.10000000 255.255.255.128 172.16.3.0/25

8 11111111.10000000 255.255.255.128 172.16.3.128/25

No of host per subnet : 27-2 = ???


VLSM (Solution C) – No need to use Class B address

No of Host

Block Size

Bits borrowed Subnet Mask Network Address

100 128 10000000 255.255.255.128 192.168.10.0/25

40 64 11000000 255.255.255.192 192.168.10.128/26

25 32 11100000 255.255.255.224 192.168.10.192/27

6 8 11111000 255.255.255.248 192.168.10. 224/29

2 4 11111100 255.255.255.252 192.168.10.232/30

2 4 11111100 255.255.255.252 192.168.10.236/30

2 4 11111100 255.255.255.252 192.168.10.240/30

2 4 11111100 255.255.255.252 192.168.10.244/30

Total IP address needed (based on Block Size) = 248


Try This!


Class B (VLSM) – 172.16.32.0/20

13


No of Host

Block Size

2x Bits borrowed Subnet Mask

Network Address

2000 2048 211 11111000.00000000 255.255.248.0 172.16.32.0/21 +8

1000 1024 210 11111100.00000000 255.255.252.0 172.16.40.0/22 +4

500 512 29 11111110.00000000 255.255.254.0 172.16.44.0/23 +2

200 256 28 11111111.00000000 255.255.255.0 172.16.46.0/24 +1

2 4 22 11111111.11111100 255.255.255.252 172.16.47.0/30 +4(e)

2 4 22 11111111.11111100 255.255.255.252 172.16.47.4/30 +4(e)

2 4 22 11111111.11111100 255.255.255.252 172.16.47.8/30 +4(e)

Class B VLSM = 172.16.32.0/20

Size : 2 12 = 4096

11111111.11111111.11110000.00000000


Route Summarization


Route summarization

• Route summarization reduces memory use on routers and routing protocol network traffic, because it results in fewer entries in the routing table (on the routers that receive the summarized routes).

• For summarization to work correctly, the following requirements must be met:– Multiple IP addresses must share the same highest-order bits.– Routing protocols must base their routing decisions on a 32-bit

IP address and a prefix length that can be up to 32 bits.– Routing updates must carry the prefix length (the subnet mask)

along with the 32-bit IP address.

CT046-3-3 Network Troubleshooting IP Addressing Revision 17

Route summarization


Route Summarization


Private Addressing and Network Address Translation

• One way to cope with the depletion of IP addresses is through the use of private addressing.

• IP addresses used on the Internet must be globally unique, usually specified by an Internet service provider.

• However, traffic that remains only on an organization's private network does not need to be globally unique, just unique across that organization's private network.


RFC1918 - Private IP Address Ranges

•Used for networks/hosts not on Internet– Class A: 1; 10.0.0.0 ~ 10.255.255.255– Class B: 16; 172.16.0.0 ~ 172.31.255.255– Class C: 256; 192.168.0.0 ~ 192.168.255.255

•Planning:– Determine which hosts are internal ONLY– Routers configured with filters


Private Addressing and Network Address Translation

• RFC1918 Private Addresses are not routed on the Internet.

• Host Computers using Private IP address space can still send and receive traffic to/from the Internet by using RFC 1631 network address translation (NAT).

• NAT can be provided by a router, firewall, or stand‑alone NAT software running on a multi‑homed server.


Static NAT – direct mapping of inside address to outside address, one to one correlation

Types of NAT


Static NAT


Dynamic NAT – outside address pulled from pool of addresses when needed then released back to pool when no longer needed, likely different address each time

Types of NAT


Dynamic NAT


PAT (Port Address Translation) – Special type of dynamic NAT where pool consists of one address, every host appears to internet as the same address, differentiated by source port number (also called Address Overloading)

Types of NAT


Overloading NAT (PAT)


Types of NAT


Network Address Translation : Example


Overloading NAT (PAT)


Q & A

l1 nwt - ip addressing-revision

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